Automatic transmission fluids are used in passenger car and commercial vehicle automatic transmissions, as well as in powershift transmissions in off-highway construction, agricultural and mining equipment, and in automotive, industrial, mobile, and marine hydraulic systems.
Three types of transmission fluids in use are DEXRON.RTM.-III primarily for General Motors transmissions, MERCON.RTM. for post-1981 Ford transmissions, and Type F (meeting Ford's M2C33F Specification) for pre-1978 and some pre-1981 Ford transmissions. DEXRON.RTM.-III went into effect on Jan. 1, 1995. Ford revised its MERCON.RTM. specification effective Jan. 1, 1994.
The foregoing specifications require automatic transmission fluids to exhibit, among other things, high frictional midpoint dynamic torque values while maintaining low delta torque values (difference between the maximum torque and the midpoint torque). The attainment of such torque values can be realized by using automatic transmission fluids containing the inventive additive combinations.
U.S. Pat. Nos. 5,053,152 discloses dispersants for use in lubricant and fuel compositions obtained by condensing a hydroxyalkyl or hydroxyaryl compound with an amine compound. These dispersants are produced by the acid catalyzed condensation of the amine reactant with the hydroxy reactant. The reference indicates that the examples disclose the preparation of dispersants with high TBN (total base number) values in the range of 45-50. The reference also indicates that lubricants and functional fluids (e.g., automatic transmission fluids) containing these dispersants can also include a zinc dialkyl phosphorodithioates.
U.S. Pat. No. 4,584,115 discloses that reaction products of boric acid or boron trioxide with epoxides having at least 8 carbon atoms are useful antiwear, friction-modifying and rust-inhibiting additives for lubricants. U.S. Pat. Nos. 4,455,243 and 4,495,088 disclose lubricating oils containing borated fatty acid esters of glycerol.
The use of phosphorus-containing amides as antiwear agents for use in lubricant compositions is disclosed in U.S. Pat. Nos. 4,032,461; 4,208,357; 4,282,171; and 4,670,169. Phosphorus-containing esters useful as antiwear agents in lubricating compositions are disclosed in U.S. Pat. No. 3,359,203. The use of such esters as E.P. agents in lubricant compositions is disclosed in U.K. Patent 1,347,845. WO 88/05810 discloses gear oil compositions which contain hydrocarbyl phosphite esters where the hydrocarbyl groups have 1 to 30 carbon atoms.
U.S. Pat. No. 4,758,362 discloses thiocarbamate additives for use in low phosphorus or phosphorus-free lubricating compositions. The additive has the formula ##STR1## wherein X is O or S, and Z is one of several listed groups. The reference indicates that these additives impart improved extreme-pressure and antiwear properties to lubricant compositions.
U.S. Pat. No. 3,702,300 discloses carboxy-containing interpolymers in which some of the carboxy groups are esterified and the remaining carboxy groups are neutralized by reaction with a polyamine having one primary or secondary amino group. These interpolymers are described as being useful as additives for use in lubricating compositions and fuels.